Joint Spatiotemporal Models for the Estimation of Prey Consumption and Predator–Prey Overlap: Dynamics of Pacific Cod Predation on Snow and Tanner Crab in the Eastern Bering Sea

ABSTRACT Pacific cod ( Gadus macrocephalus ) are important predators of juvenile snow ( Chionoecetes opilio ) and Tanner crab ( Chionoecetes bairdi ) in the eastern Bering Sea (EBS), yet the relationship between cod–crab spatial overlap and total crab consumption is only partially understood. We developed a joint spatiotemporal model that simultaneously estimates crab densities, cod densities, mass‐specific cod consumption rates of crab, and their residual covariation. From the model, we obtain spatial “predator‐expanded” consumption rates (local mass‐specific rates scaled by cod biomass) and annual, area‐integrated time‐series indices of crab consumption, cod–crab overlap, and cod and crab abundance. At local scales, spatial variation in predator‐expanded consumption rates was largely driven by mass‐specific consumption rates of crab rather than cod biomass densities. However, area‐integrated crab consumption indices were strongly related to area‐integrated indices of cod biomass, explaining > 65% of interannual variance across indices built for different cod size classes and crab species. Cod–crab overlap accounted for intermediate levels of variance (15%–17%) for consumption indices of small cod (30–60 cm) preying on large juvenile crab (2.1–4 cm carapace width) but was unrelated to indices for large cod. Other predictors, including juvenile crab abundance and the spatial extent of cold bottom waters, explained < 15% of variance, with effects varying by crab species and cod size class. The modeling framework should streamline production of overlap and consumption indices for use in population models and can facilitate understanding of natural mortality in this and other systems.